The overall objective of these studies is to investigate the degree of tumor localization by certain biologically significant cmpounds labeled with relatively short-lived radionuclides. Certain labeled compounds will be evaluated as agents for early detection of cancer, and employed in studies of normal and abnormal metabolism. These cyclotron- produced radionuclides have short half-lives which greatly reduce patient exposure, but require detection apparatus suitable for high- energy radiation. These studies will be evaluated in animals and man with quantitative scanning and imaging systems. Specific proposed studies: (1) Evaluation of Diphenylhydantoin- C11 as a Brain Scanning Agent. (2) Evaluation of Valine-C11 as a Pancreatic Scanning Agent. (3) Nitrogen-13 Compounds for Tumor and Organ Localization in Human Cancer patients. (4) Preparation and Evaluation of N13-Nitroso Compounds and F18-Haloperidol as Diagnostic Scanning Agents. (5) Studies of Se73 Compounds for Tumor Localization in Animal Models and in Human Cancer Patients.